Many of organic cathode body materials in a secondary battery have potential versus Li/Li+ of 2.0 to 3.5 V, which is lower than the potential of cathode bodies such as LiCoO2, but high energy density ensuring charging-discharging capacity of 400 to 600 mAh/g can be expected because the organic cathode body causes a plurality of electron reactions to occur.
Organic materials are low-cost and resource-saving materials unlike lithium (Li) and cobalt (Co), which are distributed unevenly. Organic materials also have advantages that design can be selected to suite intended purposes by molecular design, and that safety is ensured because activity is lost before thermal runaway occurs. As organic cathode materials, various chemical compounds have been proposed.
Patent Literatures 1 and 2 disclose organic materials having a quinone functional group as organic cathode body materials.
Patent Literatures 3 and 4 disclose organic materials called tetracyanoquinodimethane (TCNQ) and tetracyanoethylene (TCNE).
Use of organic cathode body materials for in-vehicle storage batteries and for large storage batteries for smart grids has been studied. However, organic cathode body materials have yet to be put into practical use because an irreversible secondary reaction occurs due to the radical of reaction intermediate, significant degradation occurs with the increase in the number of charging-discharging cycles due to dissolution of active material into electrolyte, and for other reasons (Non-Patent Literature 1).